1. Field of the Invention
The present invention relates to a float melting apparatus for melting a floating material by putting a material such as metal into a crucible made of a conductive material on the inside of an induction coil and making the metal float in the crucible.
2. Description of the Related Art
As the eddy current induced in metal flows in opposite directions in a crucible divided into segments in the float melting method, the forces resulting therefrom make the metal float in the crucible and cause it to be heated by its own eddy current. Since no impurities from the crucible are mixed with the molten metal, high purity liquid metal is produced. The liquid metal may be poured into a mold to manufacture products of extra high quality. The aforementioned method is employed for melting materials such as titanium and silicon. Moreover, the crucible is suitable for melting high melting-point materials because the liquid metal is free from thermal conductivity loss.
FIG. 4 is a vertical sectional perspective view of a conventional float melting apparatus. As shown in FIG. 4, there is arranged a cylindrical crucible 4 having a plurality of water-cooled copper segments 2 on the inside of a cylindrical high-frequency induction coil 1 and a bottom 3, the segments being electrically insulated from each other in the peripheral direction. When a cold metallic material 5 is put into the crucible 4 and simultaneously when power in the order of kHz is supplied from a power supply 6 to the induction coil 1, the metal 5 is caused to melt and float.
In the conventional float melting apparatus, only the upper metal portion melts and floats in the crucible, whereas the lower metal portion remains in contact with the bottom and side of the crucible. Consequently, the increased thermal loss incurred through the water-cooled crucible makes large electric power necessary to melt the metal. Moreover, the amount of liquid metal producible in one melting operation is determined by the size of the crucible. When the cold metal material is a small piece in the form of a thin metal sheet, it takes time to supply large electric power upon the principle of the proportional relationship between the size of the small piece and the intensity of the current induced therein; this makes it particularly difficult to melt a large amount of high melting-point material.